There is growing concern about the inadvertent introduction of hydrocarbons and other chemicals into the environment, and the contamination of surface water with hydrocarbons.
Hydrocarbon contamination of rain and meltwater runoff is a problem in a variety of situations, including: in parking lots and on roadways due to leaks of oil and fuel from vehicles; on rooftops having coatings that release hydrocarbons in warm weather; and in containment areas for electrical transformers, oil tanks and other facilities where large quantities of hydrocarbons are stored or used. Such containment areas typically have a perimeter dyke, such as a soil berm or concrete wall, to prevent the escape of spilled hydrocarbons from the containment area. Containment areas often also have drain systems for rain or meltwater. It is not uncommon for such containment areas to be subject to minor ongoing spills of oil and other hydrocarbons due to minor leaks, servicing of equipment etc. Such containment areas may also be subject to large spills of several thousand gallons of oil or other hydrocarbons.
Methods and apparatus for installation in drains (e.g. storm drains) for preventing hydrocarbons from entering a drainage system (and ultimately rivers and streams) are known.
Larson et al. (U.S. Pat. No. 4,302,337, issued 24 Nov. 1981) discloses an inline device for removing oil from an aqueous stream, comprising a generally coherent mass of oil-imbibing latex particles that swell as they absorb oil such that once exposed to sufficient oil, they swell to an extent that the interstitial spaces between the particles are closed and further flow of water is prevented.
The Wilcox et al patents (U.S. Pat. No. 5,391,295, issued 21 Feb. 1995; and U.S. Pat. No. 5,679,246, issued 21 Oct. 1997) disclose a hydrocarbon spill containment system comprising a housing for insertion in a drain and containing the following layers in the fluid path (going from upstream to downstream and, in the intended installation position, from top to bottom) a filter material (such as sand) in a separate permeable basket; a first geotextile layer; hydrophobic swellable polymer particles; and a second geotextile layer. The polymer particles are granular and the geotextile layers help to contain the particles. As set out in lines 21 to 24 of column 3 of the U.S. Pat. No. 5,679,246 patent, the basket and filter material provide weight on top of the polymer to force it to swell outwards (so as to seal the flow path in the presence of oil) rather than upward. The filter material also traps dirt and other small particles that would clog the polymer material.
The Gannon patents (U.S. Pat. No. 6,485,639, issued 26 Nov. 2002; and U.S. Pat. No. 6,503,390, issued 7 Jan. 2003) disclose a particular oil-targeted filtration/plugging medium (an absorbent comprising alternating units of at least two polymers selected from the group consisting of styrene, pentadiene, cyclopentadiene, butylene, ethylene, isoprene, butadiene and propylene; mixed with non-absorbent particles to provide flow channels through the absorbent); and devices for installation in a drain utilizing the disclosed or other similar filtration/plugging medium. Each of the disclosed devices includes some type of sediment/debris filter upstream of the filtration/plugging medium and porous layers to contain the filtration/plugging medium.
All of the known apparatus and methods for preventing hydrocarbon-contaminated water from entering a drainage system tend to plug the drain in which they are installed, sooner than desired, in that they plug the drains when exposed to the normal low level of oil or other hydrocarbons present in rain and meltwater runoff in containment areas etc. What is needed is an apparatus and method for preventing hydrocarbon-contaminated water from entering a drainage system that when exposed to low levels of contaminants removes the contaminants without plugging, but does plug when exposed to abnormally high levels of contaminants, such as during a major spill.